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FN2 Heavy Braking = Light Back End !

paul.goffin

paul.goffin

Messages
3,668
Had my first disappointment with the FN2 this weekend.

I was driving quite hard trying to learn the car a little more. As such I was braking hard for corners to get my speed down, before powering around the corners. As I'm still getting used to the car my cornering speed was quite low, so I was using the brakes harder than I would driving the same roads in the EP3.

On one corner I applied the brakes hard to reduce my speed and settle the car ready for the corner. But the back went light and the front almost started to snake.

Then later on a deserted unrestricted toll road ;) I was doing about 100mph when I thought I would test the brakes. This time I hit the brake peddle hard but more progressively. Again when I was at nearly max braking the back went light and the front started to lightly snake.

In both situations I very much doubt I would have experienced the snaking I did in the FN2. I know the FN2 is heavier, but I don't think it was just the weight. Maybe its the bias of the brakes is too much to the front????

Has anyone else experienced this?

Anyone got any ideas if I can improve the situation? Would improved pads on the rears help?

Or will this be a characteristic of the new Type R.
 
Could it be the effect of the Electronic Brake Distribution? On the EP3 the effects weren't really noticable until the ABS had kicked in.
Have Honda tweaked the system on the FN2 so that it shifts braking to the wheels with max grip prior to grip being lost?
 
I found the back end on my EP3 used to go light under heavy braking, but once I had changed my brake setup to the Stoptech lit on the front and the Powerslot big disc kit on the rear it was fine.

The standard brakes on the EP3 never filled me with confidence when pushing on.

Can't comment on an FN2 as I haven't driven one yet.
 
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I'm guessing it's just due to the bigger stronger brakes at the front, i can remember my EP3 doing this a couple of times. I've always wondered why Sport'ish cars have big front brakes then shitty little brakes at the rear. Is the cost really that much of a difference? :confused:
 
I never experienced it to the same extent in the EP3.

But driving a bit more today you really have to brake hard at higher speeds to notice it.

Now I know how it behaves I can drive accordingly.
 
It's to be expected. As your braking, the fronts do the most work. EG if the car weighs 1000 KG, under severe braking you have the G Force weight to consider, ie you could easily have the equivalent of 1500 KG over the front axle, which naturally makes the rear end stiffer... it happens in my ITR too, but I have noticed it on a back road where 3 figure speed would be a death warrant. I spoke to Tom at TGM about the matter and it's the same on his race cars so I wouldn't worry all that much. Perhaps the increased weight of the FN2 makes the light rear end more pronounced then what it would do in the EP3.
 
When you slam on the anchors the weight transfer pushes the cars nose hard into the ground, you get the opposite happening when you accelerate hard. Once the weight has transfered to the front of the car and the nose dips the back becomes light, it's at this point you don't want huge rear brakes or you'll lock them, which would be like pulling the handbrake on... The reason you feel the car squirming is that the rear of the car is light, so it can tramline/be effected by less than perfect road surfaces easily. This weight transfer is why you shouldn't brake hard in corners, as doing so can see you spin when the back wheels are light and have little traction.

On racing cars the brake bias is normally IRO 75% Front and 25% rear. The front wheels have incredible grip when your braking because of the extra downforce applied to them. If you yank your handbrake whilst driving slowly the braking effect is rubbish, and thats because it doesn't have that weight transfer pushing them down.

The quality of front calipers also contributes the 'wondering' under braking. My CTR did it a little when I hit the brakes hard with Spoon 4 pots on the front and OEM rears. Since returning to a more conventional setup at the front it doesn't do it. Simply because the car isn't decelerating as quickly as it was with the Spoon calipers and as such the weight transfer isn't as great.

So that's why the backend goes light in laymans terms. There are other factors to consider though, for example suspension. The Ep3 has fairly firm suspension and this is a good thing on a performance car in braking terms. When you hit the brakes hard the weight transfer from the rear to the front won't result in the car dipping as much, this means the back of the car remains more firmly in contact with ground, thus giving you a more equal and stable braking vehicle. Likewise on acceleration the rear of the car dips, you want fairly firm rear suspension or the back will dip and you'll have crap front end traction. A rear engined Porsche rockets off the line because when it accelerates it's pushing it's rear wheels into the ground aiding traction.

So if you find that the FN2 wonders more under braking than your EP3 I would suggest it's because of:

1.) It has 20mm larger rear brakes, thus the brake bias is probably more to the rear on the FN2, engineered to make use of it's heavier backend I suspect.
2.) If the front end suspension is softer for a better ride that'll also contribute.

I think that should pretty much clear everything up!
 
Thanks for that info,

I understood while the car goes light, and was slightly concerned why I felt it more in the FN2 compared to my EP3.

I hadn't realised the rears were 20mm larger, maybe that's where the extra bite comes during mild to hard braking.

So it looks like I will keep the setup as is, as you are suggesting upgrading the rears will make them lock up during heavy braking. If I upgraded the fronts it will make it worse as it will increase the weight shift under the harder braking that it would make available.
 
Curious about the rear disc size issue.

I have a photo of a Focus WRC on my bedroom wall in full tarmac spec and that has the same size discs on the rear as on the front.

I've also seen a lot of cars around with the rear discs easily the same size of the front. Come to think of it, saw a new 3 series coupe today and I couldn't help noticing how large the rears were in relation to the front.
 
More weight you have over the rear the bigger the brakes you can use on the back, so a 4WD or a RWD car will need bigger brakes at the rear as not as much weight will transfer forward. My ikkle 197 Clio had HUGE brembo 4 pots up front and only single pots on tiny disks at the back as the rear is so light that when you stand on the brakes it damn near does forward rolls!
 
Have you seen the rear discs on a Porsche Cayenne???? :eek: :eek: :eek: :eek:

They are like manhole covers!!!! :twisted: :twisted: :twisted:
 
SOates82 said:
More weight you have over the rear the bigger the brakes you can use on the back, so a 4WD or a RWD car will need bigger brakes at the rear as not as much weight will transfer forward. My ikkle 197 Clio had HUGE brembo 4 pots up front and only single pots on tiny disks at the back as the rear is so light that when you stand on the brakes it damn near does forward rolls!
Click to expand...

So huge brake upgrades are not always the way forward.
 
This is pretty normal in a FWD front engined car. All the weight pushed to the front means the back wants to overtake the rear and it unloads and will squirm a bit.

If you are more progressive with the brakes you can more stopping power before it starts wondering but theres only so much you can do! Stiffer suspension helps.
 
CTR said:
Curious about the rear disc size issue.

I have a photo of a Focus WRC on my bedroom wall in full tarmac spec and that has the same size discs on the rear as on the front.
Click to expand...

That could be put down to making the car oversteer more. Greater rear brake balance will see the backend step out, which may well suit the driver of the WRC car as they spend plenty of time sideways.

Surpised about the BMW would have though the front brakes would be at least 10% larger, as they do the majority of the braking even in a RWD car.
 
CTR_Paul said:
That could be put down to making the car oversteer more. Greater rear brake balance will see the backend step out, which may well suit the driver of the WRC car as they spend plenty of time sideways.

Surpised about the BMW would have though the front brakes would be at least 10% larger, as they do the majority of the braking even in a RWD car.
Click to expand...
You don't necessarily have to run more rear bias though. You could have the discs the same size but still setup the car so that there is more bias towards the front.
 
I think the main problem is that the FN2 has no rear independent suspension (that the EP3 had) anymore.
I noticed that breaking and going into turns is totally different to the EP3.
 
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